Recently, various apparatuses which use high voltage batteries, such as industrial equipment, home appliance, and vehicles appear. Specifically, the high voltage batteries are more actively used in a field of a vehicle technology.
A vehicle which uses an internal combustion engine using a fossil fuel such as gasoline or heavy oil as a major fuel seriously influences environmental contamination such as air pollution. Therefore, recently, people exert great efforts to develop an electric vehicle or a hybrid vehicle, in order to reduce environmental contamination.
The electric vehicle (EV) refers to a vehicle which uses an electric battery and an electric motor without using oil fuel and an engine. That is, a motor rotates by electricity accumulated in a battery to drive the vehicle. The electric vehicle was developed earlier than a gasoline vehicle. However, the electric vehicle is not commercially used due to problems such as a heavy weight of a battery and a time to charge the battery. As energy and environmental problems become serious, studies to commercialize the electrical vehicle start since the 1990s.
In the meantime, as a battery technology rapidly improves in recent years, an electric vehicle and a hybrid vehicle (HEV) which adaptively uses a fossil fuel and electric energy are commercially used.
Since the HEV uses both gasoline and electricity as a power source, the HEV is positively evaluated in view of improvement of power efficiency and reduction of exhaust gas. A main issue of the HEV is how to overcome a price difference from the gasoline vehicle. However, in the HEV, an amount of mounted secondary cells may be reduced to one third of that of the electric vehicle. Therefore, the price of the HEV may be reduced as compared with the electric vehicle, so that the HEV is expected to play an intermediate role in evolution to a perfect electric vehicle.
In the HEV and the EV which use the electric energy, a battery in which a plurality of chargeable secondary cells is formed to be one pack is used as a major power source. Therefore, the HEV and the EV has an advantage in that no exhaust gas is generated and noise is very small.
As described above, in the vehicle which uses the electric energy, performance of the battery directly affects a performance of the vehicle. Therefore, a battery management system (BMS) which not only measures a voltage of each battery cell, and a voltage and a current of the entire battery to efficiently manage to charge or discharge the battery cell but also monitors a status of a cell sensing IC which senses each battery cell to stably control the cell is acutely required.
FIG. 1 is a diagram illustrating a battery management system according to a related art.
Referring to FIG. 1, a vehicle battery management system 100 includes a battery stack 10 including a plurality of battery modules, a vehicle electrical system 20, and a battery monitoring system 30.
The battery stack 10 includes a plurality of battery modules 11 and 12. The battery modules 11 and 12 include a plurality of battery cells 13. The battery stack 10 supplies a charged high voltage DC power to the vehicle electrical system 20.
The battery monitoring system 30 includes a plurality of MCUs 31 and 32 and a BCU 33 which controls the MCUs. The battery monitoring system 30 is connected to the battery stack to monitor a charged/discharged state of the battery stack 10 and controls a charging/discharging operation of the battery stack 10.
The plurality of MCUs 31 and 32 is connected to the plurality of battery modules 11 and 12, respectively, to monitor operating characteristics of the battery modules 11 and 12 or the battery cell 13. For example, the MCU 31 monitors operating characteristics such as a voltage, a current, a charged state, or a temperature of the battery module 11 or the battery cell 13.
The plurality of MCUs 31 and 32 is connected to the plurality of battery modules 11 and 12, respectively, to control operations of the battery modules 11 and 12 or the battery cell 13. For example, the MCU 31 controls the battery module 11 or the battery cell 13 to be charged or discharged through a result of monitoring the battery module 11 or the battery cell 13.
The BCU 33 is connected to the plurality of MCUs 31 and 32 to receive information on operating characteristics of the battery modules 11 and 12 or the battery cell 13 from the plurality of MCUs 31 and 32. Further, the BCU 33 may transmit information for controlling the battery modules 11 and 12 or the battery cell 13 to the plurality of MCUs 31 and 32 based on the information received from the plurality of MCUs 31 and 32.
The plurality of MCUs 31 and 32 needs to be supplied with driving power from the outside to control the battery modules 11 and 12 and communicate with the BCU 33. Generally, the plurality of MCUs 31 and 32 is connected to a separate power supply or is supplied with low power through the BCU 33.
However, when an engine of the vehicle is turned off, the plurality of MCUs 31 and 32 does not receive the power from the BCU 33. Therefore, appropriate cell balancing of the battery modules 11 and 12 cannot be accomplished.
The plurality of MCUs 31 and 32 does not always operate. Generally, only when the plurality of MCUs 31 and 32 is in an idle mode, that is, inactive state and then it is determined that it is required to control the battery module, the plurality of MCUs 31 and 32 receives a wake-up signal from the BCU 33 to perform a control operation. Also in this case, according to the related art, the plurality of MCUs 31 and 32 is supplied with the normal power from the BCU 33 so that the power is unnecessarily consumed and efficiency of the BMS is lowered.
When the normal power is supplied to the plurality of MCUs 31 and 32, leakage/stand-by current of the battery management system (BMS) is undesirably increased.